Palliative effect of nitrate supply on ammonium injury of tomato plants: growth and chemical composition

Simultaneous supply of nitrate and high concentrations of ammonium prevented ammonium injury of tomato plants and resulted in much better growth than when tomato plants were grown on ammonium as the sole source of N. Potassium concentrations in shoots were not affected by the differences in N sources, but K accumulation was decreased in plants supplied with ammonium alone. Plants grown on ammonium with or without nitrate took up less Ca and Mg and had lower concentrations of Ca and Mg in the shoots than did plants which received only nitrate. Contents of organic acids decreased more rapidly in the shoots of plants supplied with ammonium alone than in those of plants supplied with ammonium plus nitrate. Supply of ammonium and nitrate together alleviated the rapid decrease in organic acid concentrations in the shoots of plants grown on ammonium alone.